#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
#include<math.h>
double dist(double a, double b)
{
	double d = 0;
	d = sqrt(a*a + b*b);
	return d;
}
int main()
{
	double x[10];
	double y[10];
	for (int i = 0; i < 10; i++)
	{
		scanf("%d%d", &x[i], &y[i]);
	}
	double s = 0;
	for (int i = 0; i < 10; i++)
	{
		s += dist(x[i], y[i]);
	}
	printf("distance = %.6lf", s);

	return 0;
}